The lower valve is open.
Why is the lower valve open?
So that the water may pass through and fill the vacuum above the valve.
Where are pumps mostly used?
Pumps are mostly used by people in the country, for the purpose of obtaining water from the wells which have been sunk in the earth.
When does smoke ascend through the air?
When smoke is lighter than the air, it ascends through it.
When does smoke descend through the air?
When smoke is heavier than the air, it descends through it.
Why does a cork rise to the surface of the water?